Step 1: Cook the beans. If using dried, soaked beans, drain them and put them in 5 cups of boiling water. Reduce heat to low and simmer, partly covered until the beans are tender, but still hold their shape, about 1 ½ hours. If using canned beans, drain and replace with 1 cup cold water. Combine the cooked beans with the corn, garlic, cilantro, red pepper flakes, cumin seeds, chili powder, oregano, brown sugar and salt and simmer until the flavors are blended, about 15 minutes.
Step 2: Cook the potatoes in just enough boiling water to cover until they are tender, about 20 minutes. Then mash the potatoes with butter and salt and keep warm. In a small bowl, combine the cheeses and red pepper flakes and keep them nearby.
Step 3: Preheat the oven to 400 degrees and have ready a baking sheet or roasting pan to hold the tacos. Heat 1/8 inch of vegetable oil in a skillet over medium-high heat and soft-fry the tortillas, without allowing them to become crisp, one at a time. (The tortillas should be oily and soft so they will crisp in the oven after they are filled.)
Step 4: Fill each tortilla with 1/3 cup of the mashed potatoes, 1/8 cup of the grated cheese mixture and a generous tablespoon of the chopped pepper. Roll the tortillas around the filling and secure them with toothpicks. Arrange the tacos in a single layer on the baking sheet or roasting pan and bake until the cheese has melted and the tortillas are crisp, about 18 minutes.
Step 5: While the tacos are baking, steam the chard in a covered pan over a small amount of boiling water until just tender, about 5 minutes. Puree the garlic with lemon juice and olive oil, and season with salt and pepper, then toss it with the steamed Swiss chard.